Modelling and Analysis of Global Vibroacoustic Coupling Characteristics of a Rectangular Enclosure Bounded by a Flexible Panel

The interaction between the sound field in an enclosure and its flexible panel is a critical problem; the influence of structural parameters on global vibroacoustic coupling characteristics of the panel-enclosure system is very important. In this paper, a novel index of the global coupling level was first proposed to describe the global vibroacoustic coupling extent between multiple panel vibration modes and enclosure acoustical modes of the coupled system. Then, the influence of structural parameters on global coupling levels of the coupled system with different panel boundary conditions was obtained based on the numerical results of transfer factors. Moreover, according to the comprehensive influence of the structural parameters on global coupling levels, design methods of the coupled system with low global coupling levels were then discussed. Finally, the influence mechanism of panel boundary conditions on the coupling characteristics of the coupled system was analyzed. The results show that the structural parameters have similar effect on the coupling property of the system with different panel boundary conditions. Furthermore, the influence of the structural parameters on the coupling property of the system with a clamped panel is more sensitive than that of the system with a simply supported one. Furthermore, the structural parameters, especially the enclosure depth and panel thickness, are not completely negative correlated to the global coupling levels of the system. In conclusion, this study could provide a theoretical basis for acoustical design of the panel-enclosure system (e.g., rectangular vehicle cabins) with low global coupling level, as well as the lightweight structure design of the system.

A review of self-protection deceptive jamming against chirp radars

The well-known range-Doppler coupling property of the chirp radar makes it more vulnerable to different types of deceptive repeater jammers that benefit from the pulse compression processing gain of the radar-matched filter. These jammers generate many false targets that appear before and after the true target. Therefore, the radar cannot distinguish the true target from the false ones. This paper reviews different self-protection repeater jammers and presents their pros and cons, in order to provide a reference for the study of jamming/anti-jamming methods.